1. Field of the Invention
The invention relates generally to semiconductor chip assembly technology, and more particularly, to a heat sink for a memory module and a method of manufacturing the memory module with the heat sink.
2. Description of Related Art
In general, memory module devices have advantages in that more than two semiconductor memory chips are mounted onto a single circuit board to increase memory capacity. The memory modules also overcome many inconveniences associated with mounting several individual memory chips to the circuit board. In addition, the utility of obsolete memory chips can be enhanced through the memory module. Manufacturers employing surface mount technology for producing the memory module commonly use an array of printed circuit boards where several identical boards are continuously connected.
As the operational speed of individual semiconductor chips mounted on the board increases, more and more heat is produced from the chips and hence it is important to effectively dissipate the heat. In particular, Rambus DRAMs operating at even higher speed than normal DRAMs require special concern in dissipating the heat. For example, 64M Rambus DRAMs using a printed circuit board have maximum operating power of 2.0W to 2.1W. Thus, the thermal problem is an inevitable aspect of the device. To solve the thermal problem, a heat sink can be connected to the memory module. A conventional heat sink has a Thermal Interface Material (TIM) attached to one side of the heat sink, and is fastened to the memory module. The TIM is made of silicon rubber having good thermal conductivity to transfer heat generated from the chips to the heat sink.
In coupling the heat sink to the memory module, a fastener such as a push pin or bolt is generally used. However, when the heat sink is coupled to the memory module by the push pin or by the bolt, the coupling strength of the heat sink and the memory module is weak and the reliability of the module device is poor, while memory module manufacturers and end users such as a set maker can easily disassemble or remove the heat sink from the memory module.
Further, due to the structural nature of push pins and bolts, it is difficult for the heat sink producer to supply heat sinks coupled to the fastener in advance. In addition, even when the heat sinks coupled to the fastener are supplied to the memory module manufacturer, it is difficult to stack vertically and load individual heat sinks. Also, it is difficult to develop automatic production appliances for coupling the heat sink to the memory module.
On the other hand, according to current practices of memory module manufacturers, memory modules are assembled onto an array of printed circuit boards, dummy portions of the array are removed, and electrical functions of the memory modules are tested. However, in this process, it is difficult to couple the heat sink to the memory module. In addition, it is difficult to develop an automatic appliance for automatically coupling the heat sink and the memory module.
It is an object of this invention to provide memory modules having a structure such that the heat sinks are easily coupled to the memory modules, and a manufacturing method thereof.
It is another object of this invention to provide heat sinks having a structure adapted to the automatic production of memory modules coupled with heat sinks.
According to one aspect of this invention, a heat sink is attached to a module board on which a plurality of semiconductor chips are mounted, and dissipates or spreads heat generated from the chips. The heat sink includes a coupling means for coupling the heat sink to the module board and a hole through which the coupling means pierces. The coupling means includes integrally formed first and second body portions, a flanged base integrally formed with the second body portion. An orifice is formed at least through the second body portion. The flanged base may be fixed to one side of the module board and the first body is smaller than the second body.
According to another aspect of this invention, a method for manufacturing a memory module comprises: preparing an array of printed circuit boards; preparing an individual module board by cutting the array board; stacking a predetermined number of the individual module boards; preparing a heat sink; coupling a coupling means to the heat sink and attaching a thermal interface material to the heat sink; stacking a plurality of heat sinks with the coupling means and the thermal interface material; and coupling the stacked individual module boards and the stacked heat sinks one by one.
In one embodiment of this invention, a method for manufacturing a memory module comprises: preparing an array of module boards; providing individual module boards by cutting the array board; stacking the individual module boards by a predetermined number; preparing a first plurality of heat sinks; attaching thermal interface materials and installing coupling means to the first plurality of heat sinks; stacking the first plurality of heat sinks; preparing a second plurality of heat sinks; attaching thermal interface materials to the second plurality of heat sinks; stacking the second plurality of heat sinks; and coupling, one-by-one, the first and second plurality of heat sinks to the individual module boards by using the coupling means.
In accordance with one aspect of the present invention, a heat sink for being mounted to a module board to which semiconductor chips are attached and for dissipating or spreading heat generated from the semiconductor chips is disclosed. The heat sink comprises a heat sink base; and a coupling means for coupling the heat sink base to the module board. The coupling means passes through the heat sink base. The coupling means includes integrally formed upper and lower body portions, an orifice formed at least through the lower body portion, and a flanged base formed integral with the lower body portion, the flanged base fixing the coupling means to the heat sink base. An outer dimension of the upper body portion is smaller than an inner dimension of the lower body portion.
In accordance with another aspect of the present invention, a method for stacking heat sinks for fabrication of a memory module is disclosed. The method comprises preparing lower and upper heat sinks, the heat sink comprising:
a heat sink base; and
a coupling means for coupling the heat sink base to the module board, the coupling means passing through the heat sink base,
wherein the coupling means includes upper and lower body portions, a shoulder joining the lower and upper body portions and tapering therebetween, an orifice formed at least through the lower body portion, and a flanged base formed integral with the lower body portion, the flanged base fixing the coupling means to the heat sink base, and
wherein an outer dimension of the upper body portion is smaller than an inner dimension of the lower body portion. The method further includes stacking the upper heat sinks over the lower heat sink. The upper body portion of the coupling means of the lower heat sink is inserted into the orifice formed through the lower body portion of the coupling means of the upper heat sink, and the flanged base of the upper heat sink rests on the shoulder of the lower heat sink.
These and other features, and advantages, will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings. It is important to point out that the illustrations may not necessarily be drawn to scale, and that there may be other embodiments of this invention that are not specifically illustrated.